Major utilities are once again urging state officials to make it more expensive for homes and businesses to go solar, in a last-minute effort to undermine a plan that supporters say is critical to the rooftop solar industry's future.

For months, Southern California Edison and other utilities lobbied the California Public Utilities Commission to slash the rates at which solar customers are paid for the electricity they generate, and to approve new monthly charges. Commission President Michael Picker rejected those ideas last month, proposing to leave the state's net metering program for rooftop solar customers mostly in place...